American scientists research shows that the presence of microplastics is affecting cloud formation, affecting Earth’s weather and climate.
Clouds form when water vapor, an invisible gas in the atmosphere, clings to small floating particles such as dust and turns into liquid water droplets or ice crystals. In a new study recently published by a group of scientists from the University of Chicago, it has been shown that microplastic particles can create ice crystals at temperatures 5 to 10 degrees Celsius higher than water droplets without particles. microplastics.
This suggests that microplastics in the air could influence weather and climate by creating clouds in conditions where they would not normally form.
Atmospheric chemists study how different types of particles form ice when they come into contact with liquid water. This process, which occurs continuously in the atmosphere, is called nucleation.
To see if microplastic fragments could act as nuclei for water droplets, scientists used the four most common types of plastic in the atmosphere: low-density polyethylene, polypropylene, polyvinyl chloride and polyethylene. terephthalate. Each is tested in both its pristine state and after exposure to UV, ozone and acid. All of these substances are present in the atmosphere and can affect the composition of microplastics.
They suspended microplastics in small water droplets and slowly cooled the water droplets to observe when they froze. They also analyzed the surface of the plastic fragments to determine their molecular structure, as ice nucleation may depend on the surface chemistry of the microplastic.
For most of the plastics studied, 50% of water droplets froze at -22 degrees Celsius. These results are consistent with another recent study by Canadian scientists, who also found that certain types of microplastics nucleate ice at warmer temperatures than water droplets without microplastics.
Exposure to ultraviolet light, ozone, and acids tend to reduce ice nucleation activity on particles. This suggests that ice nucleation is sensitive to small chemical changes on the surface of microplastics. However, these plastics still nucleate ice, so they can still affect the amount of ice in clouds.
According to the research team, to better understand how microplastics affect weather and climate, it is necessary to know their concentration at the altitude where clouds form. It is also important to understand the concentration of microplastics relative to other particles that can nucleate ice, such as mineral dust and biological particles, to see whether microplastics are present at comparable levels. These measurements will allow us to model the impact of microplastics on cloud formation.